Polarons and Pauli-blocking enhanced saturable absorption in MoS2 nanorod/PANI nanocomposite films

Abstract

A significant number of research studies have been performed on employing polarons originating from strong electron–lattice interactions in two-dimensional materials to realise enhanced nonlinear optical (NLO) responses. Polaronic effects have been observed in different material systems, but the correlation between specific polaronic states and NLO processes in molybdenum disulfide/polyaniline (MoS₂/PANI) nanocomposites remains to be explored. In this work, we have reported MoS₂ nanorod/PANI nanocomposites observed for their third-order nonlinear optical characteristics utilising open-aperture (OA) z-scan measurement under 532 nm nanosecond pulsed laser excitation. Pure MoS₂ revealed saturable absorption behaviour resulting from Pauli blocking near the conduction band (CB) edge in MoS₂. The introduction of MoS₂ into the PANI matrix remarkably improved the saturable absorption response. This improvement originates from significant interfacial charge transfer from the PANI polaron band to the conduction band of MoS₂. Our results demonstrate the influence of polaronic additives on the nanocomposite's overall NLO performance. Our findings offer novel perspectives into the design and development of hybrid inorganic–organic interfaces for advanced nonlinear photonics and provide potential pathways for the development of ultrafast, tunable optoelectronic and laser devices.